It is known to provide noise modification systems in motor vehicles. Such systems typically comprise one of two types—Active Noise systems, in which one or more speaker units are fitted to exhaust systems or elsewhere in a vehicle such as in the occupant cabin, and Active Exhaust systems, in which typically one or more bypass valves are provided within an exhaust system to physically alter the flow path of exhaust gasses through different parts of the exhaust system.
The speakers in Active Noise systems, in conjunction with various control means and methods, are used to provide noise waveforms, usually related to and/or derived from the ‘natural’ noise generated by the exhaust system. These noise waveforms are typically used to ‘cancel out’, minimise or suppress native exhaust notes, but may also be used to enhance them.
In Active Exhaust systems, operation of the bypass valves typically allows either a ‘normal’ exhaust note, or, when the exhaust gasses are bypassed either to a specially tuned exhaust section or such that the exhaust system becomes more akin to a ‘straight through’ system, a more ‘sporty’ (ie: louder and more aggressive, sometimes referred to as ‘throatier’) exhaust note.
In known systems, a vehicle is provided with various driving modes. Such modes may comprise, for example, ‘Normal,’ ‘Sport,’ and ‘Dynamic’ modes, but may also comprise further modes such as ‘Track’. An Active Noise or Active Exhaust system may be arranged to enhance exhaust (and/or engine) noise in certain modes (such as ‘sport’ or ‘dynamic’ modes), but in other modes (ie ‘Normal’) they are arranged to be off, or in the case of Active Noise systems even to damp or cancel out or otherwise minimise the exhaust noise. It is an aim of the present invention to provide improvements upon the prior art.